The art of aerodynamic design is one of continual change and improvement. In addition to streamline profiling of surfaces belonging to aerodynamic vehicles of ground, air and water types, a number of aerodynamic aids have been provided in the form of accessories that may be attached to vehicles at strategic locations with the idea of reducing drag on those vehicles. Air-foils of various designs are the most recognized of these products.
With respect to road transport vehicles such as semi tractor trailers and the like, the bluff profile inherent with such vehicles causes more drag when moving through air than with streamlined profiles that are not practical in production of such vehicles. Therefore, a large market exists for ways to reduce drag on such bluff-bodied vehicles to improve fuel use when the equipped vehicles are driven at certain speeds.
Aerodynamic drag on bluff-bodied vehicles consists mainly of pressure drag with skin friction created by moving air and base drag, which forms part of the total drag coefficient on the vehicle. Air-flow over bluff bodies comprises large wake production and smaller vortex shedding. The well-known Reynolds number associated with drag on small and medium vehicles falls in the sub-critical range of (1.0 to 2.0×106). Total drag force associated with such typical flow patterns is very high. A considerable amount of energy is therefore expended in overcoming such forces.
Streamlining vehicle designs is one of the most popular known methods for reducing aerodynamic drag. The effectiveness of rounding corners in design can be measured by utilizing a simple two-dimensional square section under test. The drag coefficient on such a square section at sub-critical Reynolds numbers is approximately 2.0. Maximally rounded corners improve the coefficient to a limiting factor of approximately 1.0 or a 50% reduction in drag without major design change.
Small vortex generators are known in the art, and are used in typically small aircraft to increase lift. Referring now to FIG. 1 of this specification, a vortex generator is illustrated in perspective view. Generator 100 has a base portion 101 that makes contact with the surface of a vehicle to which it is mounted and a fin portion 102 formed at a substantially upright direction from the base of the unit.
Typically, an array of such generators are arranged on a leading-edge surface of an aircraft wing to increase lift. Referring now to FIGS. 2a, 2b, and 2c, the generator of FIG. 1 is illustrated in Top, Side, and End views to better show construction. In FIGS. 2a and 2c, part of fin 102 is shown removed along an angle D for the purpose of further drag reduction in the design. Dimensions B (FIG. 2a), C (FIG. 2b) and E (FIG. 2c) can vary according to application.
An object of the present invention is to reduce drag and to increase fuel efficiency of a bluff-body vehicle through strategic alignment and positioning of vortex generators at leading edges of the vehicle. A further object of the present invention is to use the laminar flow enhanced by added vortex generators to circumvent a common problem of bug collision with windshields of such vehicles while traveling at freeway speeds.